A friend of mine let me borrow Dune 1-3. I loved them and felt I would definitely re-read Dune. When the deluxe box set of 1-3 came out I bought it but it is just sitting on my shelf. I do plan on rereading them but probably not for awhile. Sometimes I also just like having the books I’ve read on my shelf as “trophies”.
I’m more likely to buy a book that I have already re-read dozens of times for free than I am to buy a new book I haven’t read. I don’t normally find it worth it to spend money on something that I’m not sure I’d like. I also like to buy books as “trophies” as you put it. For example I got the full hardback cover set of His Dark Material with the original cover art. But whenever I feel the need to re-read them, I just do it on my Kindle lol.